The present disclosure relates generally to progressing cavity pumps, and more particularly, to a device for removing and/or installing the stator tube of a progressing cavity pump.
A conventional progressing cavity pump system, which can be used to pump a wide range of fluids, typically includes an inlet chamber or suction chamber, and a generally cylindrical stator tube having a discharge port. The pump may include a rotor and a stator located inside the stator tube and having an internal bore extending longitudinally therethrough. The rotor may be rotationally disposed in the internal bore of the stator tube. The stator may be in the form of a double lead helical nut, in which case the stator may include a pair of internal helical grooves which define the internal bore. Likewise, the rotor may be a single lead helical screw rotor including one external helical lobe. The rotor may be rotationally disposed within the internal bore so that the external helical lobe of the rotor and the internal helical grooves of the stator define a plurality of cavities therebetween. The stator is typically formed from a resilient and flexible elastomeric material, and the rotor is typically manufactured from a metallic material. The rotor may be rotatably driven by a drive shaft which may be coupled to the rotor by a universal joint as is well known to those skilled in the cavity pump art. For additional information regarding the operation and construction of progressing cavity pumps, reference can be made to U.S. Pat. No. 2,512,764, U.S. Pat. No. 2,612,845, and U.S. Pat. No. 6,120,267.
As the rotor is rotatably driven within the stator bore, the cavities formed between the rotor and the stator progress from the suction end of the stator tube to the discharge end of the stator tube. In one revolution of the rotor, two separate sets of cavities are formed, with one set of cavities being formed or opening at exactly the same rate as the second set of cavities are closing. This pumping process results in a predictable, pulsationless flow of the fluid.
Because the stator is typically made from an elastomeric material, the stator may experience wear after a period of use. Therefore, it may be desirable to remove the stator tube and stator from the progressing cavity pump system for reconditioning or replacement. Accordingly, there is a need for a device for assisting in the removal and installation of a stator tube of a progressing cavity pump.
In one embodiment, the invention is an apparatus for removing a stator tube from a position about a rotor of a progressing cavity pump, the rotor being rotatable relative to the stator tube to pump material through the stator tube. The apparatus includes an actuator assembly having a base and a piston which is displaceable relative to the base along a first axis, and a pusher rod. The base of the actuator assembly is removably attachable to a discharge end of the stator tube. The pusher rod is releasably attachable to the piston along the first axis at a plurality of locations along the pusher rod and is located to engage the rotor when the base is coupled to the stator tube, the pusher rod is coupled to the piston and the piston is driven by the, actuator assembly.
The apparatus generally operates by pulling the stator tube off of the rotor while using the rotor as a fixed ground point which provides a resistive force. By adjusting the position of the pusher rod with respect to the piston along the first axis, the actuator assembly has an adjustable working length to enable the stator tube to be removed from the rotor of the progressing cavity pump.